1. Field of the Invention
The present invention relates to high-frequency dielectric ceramic compacts for dielectric resonators, dielectric antennas, LC filters, circuit substrates and the like, used in high frequency regions, such as microwaves and millimeter waves. In addition, the present invention relates to a dielectric resonator, a dielectric filter, a dielectric duplexer and a communication apparatus using the high-frequency dielectric ceramic compact.
2. Description of the Related Art
Dielectric ceramics are being widely used for dielectric resonators, circuit substrates and the like, in high frequency regions such as microwaves.
A material used for dielectric resonators, circuit substrates and the like, is required to have the following dielectric characteristics, that is, (1) a high relative dielectric constant (∈r) in response to trend toward miniaturization since the wavelengths of electromagnetic waves in a dielectric material are shortened to 1/(∈r)1/2, (2) a small dielectric loss, that is, a high Q value, (3) stable temperature dependence of the resonant frequency, that is, the temperature coefficient (xcfx84f) of the resonant frequency is nearly 0 (ppm/xc2x0 C.), and the like.
In the recent trend toward higher frequency and higher speed in information transmission, millimeter waves tend to be used instead of microwaves. Accordingly, the devices are becoming increasingly miniaturized, and in view of processing accuracy and better workability in manufacturing, the (1) requirement described above is slightly changed in that a material having an even lower relative dielectric constant is increasingly demanded while maintaining a high Q value and stable temperature dependence of the resonant frequency.
As a dielectric ceramic compact having a relatively low relative dielectric constant, for example, there may be mentioned a MgTiO3xe2x80x94CaTiO3-based ceramic (Japanese Unexamined Patent Application Publication No. 58-166608), a Ba(Zn,Ta)O3-based ceramic (Japanese Examined Patent Application Publication No. 58-25068), a Ba(Sn,Mg,Ta)-based ceramic (Japanese Examined Patent Application Publication No. 3-34164) and an Al2O3 ceramic.
However, in the MgTiO3xe2x80x94CaTiO3-based, Ba(Zn, Ta)O3-based, and Ba(Sn, Mg, Ta)-based material, the temperature coefficient (xcfx84f) of the resonant frequency can be controlled to be 0, but the relative dielectric constant (∈r) is relatively high, such as 20 to 30.
On the other hand, the relative dielectric constant (∈r) in an Al2O3-based material is low such as approximately 10, and the Q value is high such as 400,000 to 500,000 at 1 GHz; however, the temperature coefficient (xcfx84f) of the resonant frequency is a significant negative value, such as xe2x88x9240.
An object of the present invention is to provide a high-frequency dielectric ceramic compact which can solve the problems described above and which has a relative dielectric constant (∈r) of about 20 or less and a Q value of about 20,000 or more at 1 GHz, in which the temperature coefficient (xcfx84f) of the resonant frequency can be controlled optionally about 0 (ppm/xc2x0 C.). In addition, another object of the present invention is to provide a dielectric resonator, a dielectric filter, a dielectric duplexer, and a communication apparatus using the high-frequency dielectric ceramic compact described above.
To these ends, a high-frequency dielectric ceramic compact of the present invention comprises Ba, Sb and Me which comprises Mg or Mg and at least one of Zn, Ni, and Co, wherein, when the compact is represented by the formula aBaO.bMeO.cSbO3/2 on a molar basis, the following equations hold: 0.476xe2x89xa6axe2x89xa60.513, 0.160xe2x89xa6bxe2x89xa60.175, and 0.324xe2x89xa6cxe2x89xa60.350.
In the high-frequency dielectric ceramic compact described above, the primary crystalline phase is a perovskite crystal represented by the formula Ba(Me1/3Sb2/3)O3, in which Me comprises Mg or Mg and at least one of Zn, Ni and Co.
In addition, a high-frequency dielectric ceramic compact of the present invention comprises Ba, Sb, Ti and Me in which Me comprises Mg or Mg and at least one of Zn, Ni and Co, wherein, when the compact is represented by the formula dBaO.eMeO.fSbO3/2.gTiO2 on a molar basis, the following equations hold: 0.476xe2x89xa6dxe2x89xa60.513, 0.100xe2x89xa6exe2x89xa60.175, 0.200xe2x89xa6fxe2x89xa60.349, and 0 less than gxe2x89xa60.200.
In addition, in the high-frequency dielectric ceramic compact described above, the primary crystalline phase is a perovskite crystal represented by the formula Ba{(Me1/3Sb2/3)1-xTix}O3, in which 0 less than xxe2x89xa60.4, and Me comprises Mg or Mg and at least one of Zn, Ni and Co.
A dielectric resonator of the present invention comprises a dielectric ceramic, wherein the dielectric resonator is operated by electromagnetic coupling of the dielectric ceramic with an input and an output terminal, and the dielectric ceramic comprises the high-frequency dielectric ceramic compact described above.
A dielectric filter of the present invention comprises the dielectric resonator described above and external connector(s).
In addition, a dielectric duplexer of the present invention comprises at least two dielectric filters; input/output connectors in contact with each of the dielectric filters; and antenna connector commonly in contact with the dielectric filters; wherein at least one of the dielectric filters is the dielectric filter described above.
Furthermore, a communication apparatus of the present invention comprises the dielectric duplexer described above; a transmitting circuit in contact with at least one of the input/output connectors of the dielectric duplexers; a receiving circuit in contact with at least one of the input/output connectors except the input/output connector in contact with the transmitting circuit; and an antenna in contact with the antenna connector of the dielectric duplexer.